1. Field of the Invention
The invention relates to a surgical penetrating instrument, and more particularly, the invention relates to a cannula device that penetrates a body cavity or blood vessel and secures the device in a proper position while forming a seal between the device and body cavity or vessel wall.
2. Brief Description of the Related Art
The use of cannulas or trocars to obtain vascular and/or body cavity access is becoming more frequently practiced to achieve less invasive surgical procedures. A dilator can be used in combination with a cannula to enter vessels and arteries. Dilators are surgical instruments which have a sharp tip or stylet which is used to puncture tissue to form an opening through a patient's body tissue. In operation, a tube or cannula surrounds the dilator and both are inserted together into the patient's body. The dilator is then removed, leaving the cannula behind to act as a smooth conduit or pathway for subsequent insertion of surgical tools, such as catheters, graspers, or surgical viewing apparatus. For access to a body cavity, a trocar may be used to insert a cannula into the body cavity. Several cannulas may be employed during surgery in order to simultaneously receive several surgical instruments: an organ may be grasped and manipulated through one cannula, or pathway, while a surgical scalpel cuts away tissue using another trocar, and still another cannula is used to guide viewing endoscopes.
Utilizing such surgical equipment avoids the need to make a large surgical incision and use retractors to spread the sides of the incision to provide access for performing various surgical procedures. As described above, cannulas allow surgeons to access the interior of the body during non-open chest surgery; it is less invasive and less traumatic for the patient. Further, recovery from non-open chest surgery is typically shorter.
However, known cannula and trocar assemblies must be fitted with some sealing mechanism to prevent leakages of gasses or bodily fluids through the incision after inserting such assembly during the surgical procedure. Moreover, the cannula has a tendency to slide in and out of the incision, particularly when the surgeon is trying to manipulate surgical equipment through the cannula tube into or out of the body cavity. Further, infections may develop at an incision site directly exposed to contaminants in the environment for extended periods of time.
One example of a sealing mechanism is disclosed in U.S. Pat. No. 5,549,565 to Ryan, et al. This trocar and trocar tube assembly includes a removable disposable sealing valve portion and an optional sealing ring mounted in a groove located between an external flange and a threaded cannula sleeve. The sealing valve portion includes a sealing mechanism, such as an O-ring, seated inside the cannula base, a slit valve, a universal washer, and a covering cap. The valve assembly prevents leakages after the trocar is removed and the trocar tube is left inserted to provide portal access to the interior of the body. Although the Ryan sealing valve assembly prevents leakages of gases or bodily fluids through the surgical incision, this assembly requires several independent components to perform the sealing function, and each component constitutes a potential point of mechanical failure and/or leakage.
A second example of a sealing mechanism is disclosed in U.S. Pat. No. 5,755,697 to Jones, et al. This catheterization device has two main embodiments: screw-type and moly-type. The screw-type device includes a trocar and subcutaneous sleeve with coarse spiraling threads on its outer surface. When the trocar is rotated, the cutting blade is screwed into the skin until an annular skin cup, or retaining ring, abuts the skin surface. The annular cup is concave, thereby creating a seal against the patient's skin. The spiraling threads on the sleeve, coated with a tissue promoting substance, provide sealing and self-securing capabilities for the device. An opposite end of the device from the trocar's cutting end includes fine spiraling threads securing a cap or external lumen connection to the catheterization device. The moly-type device is similar to the screw-type device; however, the deformed moly-type device holds the catheterization device in the skin rather than the combination of threading and skin tension utilized by the screw device. Although the device described in Jones, et al. prevents leakages through the skin puncture where the device is positioned, this catheterization device requires the application of a tissue promoting substance, such as Dacron, to the spiral threading to effectively seal the puncture. This substance may be difficult to remove or harm the skin while removing the device. Such a coating substance may also result in allergic reactions. Further, the conical shape of the subcutaneous sleeve tapers toward the trocar and offers little support to that portion of the device external to the body from any movement or jostling that may occur during a surgical procedure.